The present invention relates to a liquid crystal display and more particularly to a transflective liquid crystal display.
A liquid crystal display is a non-light-emitting type display that displays a picture by adjusting an amount of transmitted light differently from a self-light-emitting type display represented by a cathode ray tube (CRT) and a plasma display panel (PDP). The liquid crystal display is characterized by thinness, light weight and low power consumption.
As the liquid crystal display, there are a transmissive liquid crystal display that has a light source (hereinafter referred to as backlight) disposed at the back thereof and can adjust an amount of transmitted light from the light source to display a picture and a reflection liquid crystal display that utilizes external light such as indoor illumination and sunlight and makes the external light enter the display from the surface thereof so that an amount of reflected light of the external light can be adjusted to display a picture. Furthermore, there is a liquid crystal display (hereinafter referred to as transflective liquid crystal display) that can be used as a reflection liquid crystal display in light surroundings and be used as a transmissive liquid crystal display in dark surroundings. The transflective liquid crystal display has the reflection type and transmission type display functions and can put off the backlight in light surroundings to thereby reduce the power consumption. In addition, the backlight can be turned on to thereby obtain the visibility in dark surroundings. That is, the transflective liquid crystal displays are suitable for liquid crystal displays used in portable apparatuses such as portable telephones and digital cameras supposed to be used in various surroundings.
The transflective liquid crystal display is required to arrange a transmission area and a reflection area in a pixel independently and design respective retardations in the transmission and reflection areas optimally as described in JP-A-2000-187220. This requirement is achieved by providing a step in the reflection area and reducing the thickness of a liquid crystal layer in the reflection area to about half of that in the transmission layer.
Further, in the transmissive liquid crystal display of the vertical alignment (hereinafter abbreviated to VA) system, as described in JP-A-2004-38165, the pixel is divided into two areas to make the two areas have different electro-optical characteristics, so that the γ-shift in case where the display is observed from the oblique direction is reduced. The γ characteristic is expressed by a numerical value representing the gradation or gray scale characteristic and when the numerical value is different in the observation direction, it is shown that the gradation is different depending on the observation direction.